Ozone is produced from oxygen by silent discharge or by the action of ultraviolet rays below a critical wavelength. Above all, ozone is produced by irradiating oxygen with an ultraviolet ray of a wavelength smaller than 200 nm, preferably of a wavelength of 185 nm, according to the following formulas (I) and (II). EQU O.sub.2 +hv.fwdarw.20 (I) EQU O.sub.2 +0+Ml.fwdarw.O.sub.3 +Ml (II)
wherein hv is an ultraviolet ray and Ml is a third substance such as nitrogen.
For deodorization, there has thus far been adopted a method of decomposing malodorous substances in exhaust gases by oxidation with the produced ozone and treating unreacted ozone with activated carbon in consideration of its toxicity to human bodies. In order to improve the efficiency of deodorization by ozone, it has been known to use oxygen of nascent state with extremely strong oxidizing power, which is produced by forcibly decomposing ozone. The means for producing the nascent state oxygen from ozone include catalytic methods, ultraviolet (above a critical wavelength) ray methods, pyrolytic methods, radioactive ray or electron beam irradiation methods and other methods using supersonic or high freguency waves. As deodorizing devices using the radioactive ray or electron beam irradiation or supersonic or high freguency waves are relatively large in scale, it appears practically advantageous to use a catalyst or ultraviolet ray for deodorizers of small sizes which are intended for home use.
The decomposition of ozone by a catalyst is generally expressed by the following formula (III). EQU O.sub.3 +M.sub.2 .fwdarw.O.sub.2 +(O) +M.sub.2 (III)
wherein M.sub.2 is a catalyst, (O) is oxygen in nascent state.
The decomposition of ozone by ultraviolet ray is generally expressed by the following formula (IV) EQU O.sub.3 +hv.fwdarw.O.sub.2 +(O) (IV)
In the catalytic ozone decomposition, however, it has been difficult to maintain the initial high decomposition capacity since the catalyst life is shortened as it is rapidly deteriorated due to oxidation reaction of the catalyst itself as a result of the ozone decomposition. In case of ozone decomposition by an ultraviolet ray with a wavelength of 254 nm, the decomposition capacity is impractically low as compared with the catalytic method.